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©2009 Waters Corporation | COMPANY CONFIDENTIAL©2011 Waters Corporation

How To Maintain the Performanceof Your MS System

Stefan BergvallSweden

Båstad 2011-11-09

©2011 Waters Corporation 2

Contamination

Common contaminations— If we know what it is, it is easier to

remove

Source of contamination— To prevent the same mistake from

happening twice

Cleaning of contamination — How do we remove them?

Control contaminationLess ion suppression => increased S:N => lower LOQLess isobaric interference => Good accurate mass data

=> ☺


Contamination

Polyethylene Glycol (PEG) or PEG-Like MaterialsMetal ionsPhthalatesSiloxanesGrease /oilsSurfactants


Polyethylene Glycol (PEG)

Description— Polymer series

Sources of PEG— Organic solvents— MS calibration solutions— Hand cream— Sample detergents— Glassware (dishwashing detergents)— Cleaning solutions from manufacturing

Mass in ES+ of delta m/z=44


Metal Ions

Sodium and PotassiumIron— Sources

o Water and acetonitrileo Acetic acid (lower in formic acid)o Non-passivated stainless steel parts

Nickel— Source

o Hastelloy C-276 metal used in solvent filters


Metal Ions

Molybdenum— Molybdenum adducts of ACN + FA + H2O— m/z = 240— Sources

o Hastelloy C-276 metal used in solvent filters


Phthalates

PlasticizerCommon phthalates include:

o Di-2-ethylhexyl phthalate (DEHP) [M+H] = 391o Diisodecyl phthalate (DIDP) [M+H] = 447o Diisononyl phthalate (DINP) [M+H] = 419o Diisooctyl phthalate (DIOP) [M+H] = 391

Adducts formed for Diisooctyl phthalate (DIOP)o [M+Na]+ = 413o [M+K]+ = 429o [2M+NH4]+ = 798o [2M+Na]+ = 803

— Phthalic anhydride m/z =149 prevalent fragment observedSources

o Water and organic solvents that have come in contact with plasticso Extracted from plastic tubing, water storage containers, vials, capso Laboratory air


Phthalates

Spectra showing common phthalate contaminants

Diisononyl phthalate (DINP)C26H42O4

Diisooctyl phthalate (DIOP)

C24H38O4

Diisodecyl phthalate (DIDP)C28H46O4


MRM chromatograms combined withMS scan

MRM chromatogram + MS chromatogramExtract spectra at 2.45 minutes

SpectrumSuspect 510.39 iondouble–click to extractmass chromatogram


Reduce ion supression by separating contaminant from analyte

510.39 ion elutes at same r.t. as compound in MRM channel

Masschromatogram of 510.39

Improve separation by lower gradient slope

⇒intensity increases 40% on MRM⇒due to less ion supression


Minimizing background ions

Solvents and additives

— Some HPLC grade solvents might contain PEG. PEG is not seen by a UV detector, but will be observed using an MS. Always read the label

— Some HPLC grade solvents contain metal ions

— Fresh solvents are better than previously opened bottles

— Additives should also be pure. 90% formic acid solution contains 10% other compounds! Analytical grade (>99%) is recommended

— Use ultrapure (i.e., particle-free, chemically clean, 18-megaohm cm resistivity) water.


Minimizing background ions

Vials, caps, well plates

— Vial caps with septa may contain plastics or adhesives

— Well plate glue-on foil covers may leachadhesives

Glassware

— Washing in a common dishwashing facility can contaminate glassware with detergent residues (PEG-like compounds) and surfactants

— Rinse only with mobile phase quality solvents that will be used

Plastic containers or tubing

— Storage of solvents or water in plastic is NOT recommended

Vials tested for chemical cleanliness and low absorption


Cleaning of contamination

Mixture 1: — General wash:

25:25:25:25 ACN:H20:MeOH:IPA + 0.2% FAflush with e.g. ACN:H2O 10:90 afterwards

Mixture 2:— PEG wash:

50% ACN, 49% H20 + 1% Ammonium hydroxide flush with e.g. ACN:H2O 10:90 afterwards

Mixture 3: — 30% Phosphoric acid

o Flush with H2O then with mobile phase• Disconnect MS and column


Solvents

Highgrade Acetonitrile or Methanol

— Highest chemical purity and particle-free (prefiltered by the manufacturer with 0.2 micron filter)

— Recommended sources: J.T. Baker®: LC/MS Grade, B&J Brand® LC/MS Grade, or Fisher: Optima® LC/MS Grade

— Increased uptime, seals and plungers last longer— Less contamination— Do NOT filter already filtered solvents— Always use fresh bottles, avoid putting the solvent filters on

the table


Solvents and additives

Avoid hastelloyfilters (contamination-clusters with Mo, Ni)

— Stainless steelfilters for Quads (Partnr:700003616)

— Titanium-filters for High resolution instruments (Partnr:700003530)

Use the lowest possible concentration of mobile phase additive (e.g., 0.1% formic acid, not 1%)Use the highest quality of additives available. Use additives (for example, formic acid) that have low concentrations of iron and other metal ions. Acetic acid can contain a significant amount of iron and other metal ions


Reference information


MS Maintenance

Likely locations for MS contamination are front end components:— ESI probe (probe tip, capillary, unions)— Sample cone— Lockspray baffle — Ion source block— Source enclosure — PEEK tubing connecting column outlet to API source — Components of the divert/injection valve or split (if fitted)— PEEK support block— First ion guide (or hexapole) — LC tubing— Nitrogen gas tubing or Nitrogen gas source (e.g., generator)


MS Maintenance

Cleaning of sample cone— What samples have been introduced? Proteins? Salts?— Chemicals used are dependent of what has been introduced

o H2O, MeOH, FA, IPA, ACN, DCM etc.— Easy contamination

o Sonicate in MeOH for 15-30 mins, dry with N2-gas— General clean

1. Sonicate in 10% FA in 50/50 MeOH/H2O for ~15 mins2. Rinse with H20 to remove residues of FA3. Sonicate in MeOH for ~15 mins4. Dry with N2-gas

— Heavy contaminationo Fiber brush peno Cotton stickso Last resort, 5M HNO3

Partnr: 0901018

AVOID fiber brush on inner sample cone

Ok to use fiber brush onouter sample

cone


MS Maintenance

Hexapole cleaning— Easy contamination, sonicate in MeOH for 30 mins,

dry with N2-gas— Heavy contamination, sonicate in MeOH + 10% FA,

rinse with H2O and sonicate in MeOH for 10 mins, dry with N2-gas

T-Wave— Sonicate in MeOH for 30 mins,

dry with N2-gas

Sonicate in MeOHor MeOH+10%FADry with N2-gasRemove differential plate

Sonicate in MeOH, AVOID FA or

chlorinated solvents


System test

Testmix— Retentiontime

o Pump ok?

— Reproducibilityo Injector and MS ok?

— Accurate masso Calibration needed?

— Reduces servicetime


Test Mix Chromatogram

400 pg/uL in 80:20 H2O:ACN

Component Empirical Formula

Exact Mass (as [M+H]+)

Exact Mass (as [M-H]-

)

Acetaminophen C8H9NO2 152.0712 150.0555

Caffeine C8H10N4O2 195.0882 193.0726

Sulfaguanidine C7H10N4O2S 215.0603 213.0446

Sulfadimethoxine C12H14N4O4S 311.0814 309.0658

Val-Tyr-Val C19H29N3O5 380.2185 378.2029

Verapamil C27H38N3O4 455.2910 453.2753

Terfenadine C32H41NO2 472.3216 470.3059

Leucine Enkephalin

C28H37N5O7 556.2771 554.2615

Reserpine C33H40N2O9 609.2812 607.2656

Erythromycin C37H67NO13 734.4691 732.4534


Injector

Wash solvents (When using Partial loop with needle overfill)

— Strong wash: 25:25:25:25 ACN:MeOH:H2O:IPA + 1-2%FA— Carryover issues:

o Weak wash as above, strong wash 2% ammonia instead of FA=>Lower carryover => lower LOQ

Different needles depending on samples

205000369 700002644 205000362

FEP/Metal Peek Stainless steel PEEKsilTM

700002708


Spare Parts

Good to have on the shelf to increase uptime and quality:— Capillaries for probe of interest— Spare sample cone— Checkvalves for pump— Different types of needles— Loops of different sizes

E-mail [email protected] if you are interested in a document with spareparts and partnumbers good to have on your shelf


Parts Locator


Questions?

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